1. Field of the Invention
The present invention relates to a GPS (Global Positioning System) receiver for automatically messaging a measured location to the user using the GPS, a GPS management station thereof, and a location messaging system thereof.
2. Description of the Related Art
A location messaging system using a GPS receiver has become common. The location messaging system messages a measured location to the user. The GPS receiver receives spectrum spread signals of for example ephemeris data and almanac data from each of several to ten and several satellites and obtains location information (latitude and longitude). The almanac data is used to decide a satellite that the receiver can acquire. On the other hand, the ephemeris data is accurate location information of the acquired satellite and is used to obtain the distance between the receiver and the acquired satellite.
The GPS receiver receives data from for example three satellites and calculates its pseudo position corresponding to turnaround time of each data. In addition, the GPS receiver receivers data from a fourth satellite, corrects an error of the pseudo distance, and obtains its current location.
In recent years, the GPS have been proposed for messaging the location of a prowling aged person to a guardian and for tracking a stolen car. To use the GPS for such purposes, the power of the GPS receiver should be always turned on. Alternatively, as the user requires, the GPS receiver should be remotely turned on so as to obtain the location information thereof. Since the GPS receiver performs a large number of calculations for obtaining location information corresponding to received data, the power consumption of the GPS receiver is large. Thus, when the GPS receiver is used in a portable unit, it is not practical to always turn on the power of the GPS receiver. Consequently, the GPS receiver should be remotely controlled.
However, since a conventional GPS receiver does not have an automatic call receiving means or a received call recognizing means, it is difficult to remotely control the GPS receiver. A GPS receiver that can automatically originate a call to a particular telephone number has been disclosed in Japanese Patent Laid-Open Publication No. 7-240964 as a portable security apparatus. However, this GPS receiver cannot automatically receive a call. Thus, since the GPS receiver cannot be polled, it cannot be managed by a center station. In addition, the location of the GPS receiver cannot be passively and remotely obtained.
In an information transmitting means of a GPS receiver as the above-described related art reference of Japanese Patent Laid-Open Publication No. 7-240964, titled xe2x80x9cPortable Security Apparatusxe2x80x9d, and another related art reference of Japanese Patent Laid-Open Publication No. 8-280052, titled xe2x80x9cMessage Data Transmitting/Receiving System, Message Data Transmitting/Receiving Apparatus, and Message Data Receiving Apparatusxe2x80x9d, a DTMF (Dial Tone Multi-Frequency) signal is transmitted as a push-phone tone signal. However, although these apparatuses have a data transmitting/receiving means, they do not have a data recognizing means. Thus, in these related art references, it is difficult to remotely control the GPS receiver.
In the related art references, since it is difficult to remotely control the GPS receiver, there are various problems. For example, in the conventional GPS receiver, a dialer can be automatically operated. However, to activate the dialer, a button or an emergency switch of the GPS receiver should be manually operated. Thus, the conventional GPS receiver cannot be non-attendantly or automatically operated.
In addition, since the conventional GPS receiver does not have the automatic call receiving means and the data recognizing means, the base station cannot set the operation of the GPS receiver and remotely control it. Moreover, the base station cannot set a hazard area to the GPS receiver and remotely turn on/off the power thereof. In particular, since the power consumption of the GPS receiver is large, the power of the GPS receiver should be remotely controlled. However, the conventional technologies do not satisfy such requirements.
As an information transmitting means of the GPS receiver, a DTMF signal is preferably used from viewpoints of its simplicity and communication path. In other words, a DTMF signal generating means disposed in the GPS receiver can be used. Thus, an existing analog line can be selected as a communication path. Moreover, in a digital portable telephone network, the DTMF signal can be used as digital data code thereof in the network. Thus, the reliability of the analog line is further improved. On the other hand, many types of information can be obtained from the GPS (for example, the latitude and altitude of the GPS receiver, the speed and traveling direction of the GPS receiver, the current time, and so forth). Thus, it is not proper to transmit all types of information as a DTMF signal obtained form the GPS receiver from viewpoints of transmission time and reliability. In addition, since the conventional technologies do not allow the GPS receiver to be remotely controlled, the contents of the transmission data are fixed.
Thus, in the conventional GPS receiver that receives data as a DTMF signal, only location information of latitude and longitude is obtained as GPS information to be transmitted. Conventionally, information such as the speed and traveling direction of the GPS receiver that is obtained as GPS information is discarded. In the conventional method, to obtain such information, the GPS receiver should frequently transmit location information to the base station. The base station should calculate the speed and traveling direction of the GPS receiver with the location information received therefrom. Thus, in the system, the communication time and communication interval become large. In addition, the base station should perform a history management for each GPS receiver.
In addition, the conventional GPS receiver does not have a receiving function for other than GPS data. Thus, the base station cannot transmit for example basis information of almanac data to the GPS receiver. The GPS receiver acquires a satellite and measures the latitude and longitude of the location of the GPS receiver corresponding to the almanac data. Thus, when the power of the GPS receiver is turned off for a long time or almanac data cannot be received from a satellite for a long time, the almanac data should be received from the satellites and downloaded to the GPS receiver. However, it takes around 20 minutes to download the almanac data. Thus, the GPS receiver cannot be quickly re-started.
The GPS receiver can receive data from satellites in an area free of obstacles (for example on a sea). Thus, the GPS receiver can always measure the latitude and longitude thereof. In contrast, in a town or a valley where there are full of obstacles, since the GPS receiver cannot properly receive data from satellites, it cannot accurately measure its location. In this case, the GPS receiver should use the latest location information measured one second before.
However, in the conventional technologies, information as a DTMF signal obtained from the GPS receiver is limited to location information of the latitude and longitude thereof. Thus, measured time data (time stamp) cannot be obtained. Consequently, the GPS receiver cannot determine whether location information is new information or old information (for example, several hours before). In other words, the basic reliability of the location messaging means of a mobile substance is low.
An object of the present invention is to provide a GPS receiver, a GPS management station, and a location messaging system that allow the location of the GPS receiver to be remotely, automatically, and accurately measured.
A first aspect of the present invention is a GPS receiver for receiving navigation messages from a plurality of satellites and measuring the location of the GPS receiver corresponding to the received navigation messages, comprising a signal processing means for receiving signals from the satellites, extracting navigation messages from the signals, and measuring the location of the GPS receiver corresponding to the extracted navigation messages, and a transmitting means for adding time information at which each of the navigation messages was extracted to the relevant navigation message and transmitting the resultant data to the outside of the GPS receiver.
A second aspect of the present invention is a GPS management station for managing a GPS receiver that receives navigation messages from a plurality of satellites and measures the location of the GPS receiver corresponding to the navigation messages and for downloading the navigation messages received from the satellites, comprising a means for transmitting a control signal to the GPS receiver so as to control the GPS receiver, and a means for receiving navigation messages with time information at which the navigation messages were extracted from the GPS receiver.
A third aspect of the present invention is a location messaging system, comprising a GPS receiver for receiving navigation messages from a plurality of satellites and measuring the location of the GPS receiver corresponding to the received navigation messages, the GPS receiver having a signal processing means for receiving signals from the satellites, extracting navigation messages from the signals, and measuring the location of the GPS receiver corresponding to the extracted navigation messages, and a transmitting means for adding time information at which each of the navigation messages was extracted to the relevant navigation message and transmitting the resultant data to the outside of the GPS receiver, and a GPS management station having a means for transmitting a control signal to the GPS receiver so as to control the GPS receiver, and a means for receiving navigation messages with time information at which the navigation messages were extracted from the GPS receiver.
A fourth aspect of the present invention is a location messaging system, comprising a GPS receiver for receiving navigation messages from a plurality of satellites and measuring the location of the GPS receiver corresponding to the received navigation messages, the GPS receiver having a signal processing means for receiving signals from the satellites, extracting navigation messages from the signals, and measuring the location of the GPS receiver corresponding to the extracted navigation messages, and a transmitting means for adding time information at which each of the navigation messages was extracted to the relevant navigation message and transmitting the resultant data to the outside of the GPS receiver, a GPS management station having a means for transmitting a control signal to the GPS receiver so as to control the GPS receiver, and a means for receiving navigation messages with time information at which the navigation messages were extracted from the GPS receiver, and an information unit for communicating with the GPS management station.
A fifth aspect of the present invention is a GPS management method for managing a GPS receiver that receives navigation messages from a plurality of satellites and measures the location of the GPS receiver corresponding to the navigation messages and for downloading the navigation messages received from the satellites, comprising the steps of transmitting a control signal to the GPS receiver so as to control the GPS receiver, and receiving navigation messages with time information at which the navigation messages were extracted from the GPS receiver.
A sixth aspect of the present invention is a location messaging method of a system having a GPS receiver for receiving navigation messages from a plurality of satellites and measuring the location of the GPS receiver corresponding to the received navigation messages, and a GPS management station, the location messaging method comprising the steps of causing the GPS receiver to receive signals from the satellites, extract navigation messages from the signals, and measure the location of the GPS receiver corresponding to the extracted navigation messages, causing the GPS receiver to add time information at which each of the navigation messages was extracted to the relevant navigation message and transmit the resultant data to the outside of the GPS receiver, causing the GPS management station to transmit a control signal to the GPS receiver so as to control the GPS receiver, and causing the GPS management station to receive navigation messages with time information at which the navigation messages were extracted from the GPS receiver.
A seventh aspect of the present invention is a location messaging method of a system having a GPS receiver for receiving navigation messages from a plurality of satellites and measuring the location of the GPS receiver corresponding to the received navigation messages, a GPS management station, and an information unit, the location managing method comprising the steps of causing the GPS receiver to receive signals from the satellites, extract navigation messages from the signals, and measure the location of the GPS receiver corresponding to the extracted navigation messages, causing the GPS receiver to add time information at which each of the navigation messages was extracted to the relevant navigation message and transmit the resultant data to the outside of the GPS receiver, causing the GPS management station to transmit a control signal to the GPS receiver so as to control the GPS receiver, causing the GPS management station to receive navigation messages with time information at which the navigation messages were extracted from the GPS receiver, and causing the GPS management station to transmit the location information of the GPS receiver corresponding to the navigation messages to the information unit.
As described above, the GPS receiver according to the present invention measures the location thereof corresponding to navigation messages received from satellites and transmits the navigation messages to the outside along with time information of the navigation messages. Thus, the receiving side of the navigation messages can compensate the measured results corresponding to the time information. Consequently, the receiving side can more accurately obtain the position information.
In addition, since the GPS management station according to the present invention transmits a control signal to the GPS receiver, the GPS management station can remotely controls the GPS receiver.
In the location messaging system according to the present invention, the GPS receiver measures the location thereof corresponding to navigation messages received from satellites and transmits the navigation messages to the outside along with time information of the navigation messages. The GPS management station that manages the GPS receiver receives the navigation messages and the time information thereof and transmits a control signal to the GPS receiver. Thus, the GPS management station can compensate the measured results of the GPS receiver corresponding to the received time information. In addition, the GPS management station can remotely control the GPS receiver.
In the location messaging system according to the present invention, the GPS receiver measures the location thereof corresponding to navigation messages received from satellites and transmits the navigation messages to the outside along with time information of the navigation messages. The GPS management station that manages the GPS receiver receives the navigation messages and the time information thereof and transmits a control signal to the GPS receiver. In addition, the GPS management station communicates with an external information unit. Thus, the GPS management station can compensate the measured results of the GPS receiver corresponding to the received time information. In addition, the GPS management station can remotely controls the GPS receiver corresponding to communication with the information unit. Moreover, the GPS management station can transmit the measured results to the information unit.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.